It is known to use a synchronous modem or data communications equipment ("DCE") to synchronously transmit data signals to a communications channel at a fixed rate. In a typical arrangement, the synchronous DCE will first receive data signals from a synchronous terminal or data terminal equipment ("DTE"), store the data signals in a buffer, and thereafter transmit the data signals to the channel. (In what follows, the term "DTE" is used interchangeably with "terminal"; also, the term "DCE" is used interchangeably with "modem.")
In such arrangements, the modem receives the data from the terminal at the same rate used by the modem to transmit data to the channel, that is, the channel rate. Thus, the flow of signals between the terminal and the modem must equal the channel rate. If the optimum rate for the terminal and modem to exchange data is significantly different from the channel rate, this results in the modem and/or the terminal being forced to operate at an inefficient rate. What is needed, therefore, is a method which would allow the modem to control the flow of data signals from the terminal. With such an arrangement, the modem and the terminal would be able to exchange data signals at a bit rate different from the rate of the synchronous channel.